Battery packs for portable electronic products are typically subject to repeated number of drops. In particular, users of portable communication products such as two-way radios, cordless telephones, and cellular phones tend to drop their portable products, causing the problem of intercell contact intermittency. This temporary loss of power due to a broken connection causes unpredictable device operation, or in the case of a device with volatile memory circuits, a total loss of the memory's contents. This problem could potentially cause the loss of communications and/or other functions in other portable electronic products as well.
A battery can comprise of a single battery cell or a plurality of battery cells arranged in a stick fashion, or end-to-end, for example. A contacting scheme is required to reliably connect the battery cells between themselves and with the external electronic circuitry in the electronic device during all modes of operation. Battery cells are often cylindrically or rectangularly shaped and include positive and negative electrical contact surfaces at their opposed ends respectively. Consequently, the battery cells are coupled together to form batteries generally located in a cylindrical chamber or a rectangular chamber formed within a battery housing. To contact a battery, present embodiments require that conductive contacts be placed at opposite ends of the cylindrical or rectangular chamber so as to electrically and mechanically contact the respective positive and negative battery terminal surfaces of the battery situated in the chamber. Using conventional spring contacting methods, a conductive spring that compresses when the battery is inserted is situated at one end of the chamber. The spring force exerted by the contact acts to retain the battery against an opposing contact which is typically located on the opposite end of the battery.
For the production of battery packs where the cells are placed end-to-end, intercell connections such as welds are often used between cells to prevent the plurality of battery cells from being permanently dislocated or displaced due to a vibration or a drop of the electronic device. The intercell connections are necessary since typically the contact spring force of the spring contact at the end of the cell string is not high enough to overcome the high frictional forces required to eliminate the internal rattle of the cells during vibration or a drop.
The need to eliminate the problem of intercell contact intermittency is even greater today, since the trend in manufacturing of battery packs is toward a weldless battery design. In addition, manufacturing cycle time would be reduced with the eliminated step to spot weld battery cells together in a battery pack since welding is an inefficient manufacturing step. However, intercell contacts still continue to be welded due to the unreliability of weldless batteries. Thus, the trend towards weldless battery packs will move forward as the risk of intercell contact intermittency diminishes. Therefore, a need exists for a battery pack, particularly a weldless battery, that will endure repeated drop conditions and eliminate the problem of intercell contact intermittency.